A dicot plant lacking cotyledons is
Cuscuta
A. Cuscuta- Dodder is parasitic on a very wide variety of plants, including a number of agricultural and horticultural crop species, such as alfalfa, lespedeza. It has no cotyledons.
B. Santalum is a genus of woody flowering plants, the best known and commercially valuable of which is the Indian sandalwood tree. It has two cotyledons.
C. Lodoicea, commonly known as the sea coconut, it has one cotyledons.
So, the correct answer is 'Cuscuta'.